docs: def _explain(self, tree):
          """ Set up the engine to do a dry run of a query """
          self._explaining = True
          self._call_list = []
          old_call = self.connection.call
  
          def fake_call(command, **kwargs):
              """ Replacement for connection.call that logs args """
              if command == "describe_table":
                  return old_call(command, **kwargs)
              self._call_list.append((command, kwargs))
              raise ExplainSignal
  
          self.connection.call = fake_call
          try:
              ret = self._run(tree[1])
              try:
                  list(ret)
              except TypeError:
                  pass
          finally:
              self.connection.call = old_call
              self._explaining = False